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Background: Atrial septal defect and Impella have been proposed for left ventricular unloading in venoarterial extracorporeal membrane oxygenation patients. This work aims at evaluating the haemodynamic changes in venoarterial extracorporeal membrane oxygenation patients after Impella implantation or atrial septal defect realization by a simulation study., Methods: A lumped parameter model of the cardiovascular system was adapted to this study. Atrial septal defect was modelled as a resistance between the two atria. Venoarterial extracorporeal membrane oxygenation and Impella were modelled starting from their pressure-flow characteristics. The baseline condition of a patient undergoing venoarterial extracorporeal membrane oxygenation was reproduced starting from haemodynamic and echocardiographic data. The effects of different atrial septal defect size, Impella and venoarterial extracorporeal membrane oxygenation support were simulated., Results: Impella caused an increment of mean arterial pressure up to 67%, a decrement in mean pulmonary arterial pressure up to 8%, a decrement in left ventricular end systolic volume up to 11% with a reduction up to 97% of left ventricular cardiac output. Atrial septal defect reduces left atrial pressure (19%), increases right atrial pressure (22%), increases mean arterial pressure (18%), decreases left ventricular end systolic volume (11%), increases right ventricular volume (33%) and decreases left ventricular cardiac output (55%)., Conclusion: Impella has a higher capability in left ventricular unloading during venoarterial extracorporeal membrane oxygenation in comparison to atrial septal defect with a lower right ventricular overload.

Introduction: To develop and test a lumped parameter model to simulate and compare the effects of the simultaneous use of continuous flow (CF) and pulsatile flow (PF) ventricular assist devices (VADs) to assist biventricular circulation vs. single ventricle circulation in pediatrics., Methods: Baseline data of 5 patients with biventricular circulation eligible for LVAD and of 5 patients with Fontan physiology were retrospectively collected and used to simulate patient baselines. Then, for each patient the following simulations were performed: (a) CF VAD to assist the left ventricle (single ventricle) + a PF VAD to assist the right ventricle (cavo-pulmonary connection) (LCF + RPF); (b) PF VAD to assist the left ventricle (single ventricle) + a CF VAD to assist the right ventricle (cavo-pulmonary connection) (RCF + LPF)., Results: In biventricular circulation, the following results were found: cardiac output (17% RCF + LPF, 21% LCF + RPF), artero-ventricular coupling (-36% for the left ventricle and -21.6% for the right ventricle), pulsatility index (+6.4% RCF + LPF, p = 0.02; -8.5% LCF + RPF, p = 0.00009). Right (left) atrial pressure and right (left) ventricular volumes are decreased by the RCF + LPF (by RPF + LCF). Pulmonary arterial pressure decreases in the LCF + RPF configuration. In Fontan physiology: cardiac output (LCF + RPF 35% vs. 8% in RCF + LPF), ventricular preload (+4% RCF + LPF, -10% LCF + RPF), Fontan conduit pressure (-5% RCF + LPF, +7% LCF + RPF), artero-ventricular coupling (-14% RCF + LPF vs. -41% LCF + RPF) and pulsatility (+13% RCF + LPF, - 8% LCF + RPF)., Conclusions: A numerical model supports clinicians in defining and innovating the VAD implantation strategy to maximize the hemodynamic benefits. Results suggest that the hemodynamic benefits are maximized by the LCF + RPF configuration.

The analysis of the efficiency and optimum use of cardiovascular and respiratory support systems is of great importance in research and development as well as in clinical practice. To understand the complex interaction between human cardiovascular or respiratory systems and the mechanical assist devices, a number of physical, computational or hybrid (physical-electrical or physical-computational) models/simulators have been developed and used in recent years. The hybrid models combine the advantages of both the physical models (interaction with assist devices) and of the computational/electrical models (accuracy, flexibility). This paper reviews the existing solutions and briefly describes their characteristics, advantages and disadvantages, chiefly emphasizing the features of the hybrid models that are most promising for future development.

Background: Right ventricular failure (RVF) is one of the major complications during LVAD. Apart from drug therapy, the most reliable option is the implantation of RVAD. However, BIVAD have a poor prognosis and increased complications. Experiments have been conducted on alternative approaches, such as the creation of an atrial septal defect (ASD), a cavo-aortic shunt (CAS) including the LVAD and a cavo-pulmonary connection (CPC). This work aims at realizing a lumped parameter model (LPM) to compare the acute hemodynamic effects of ASD, CPC, CAS, RVAD in LVAD pediatric patients with RVF., Methods: Data of 5 pediatric patients undergoing LVAD were retrospectively collected to reproduce patients baseline hemodynamics with the LPM. The effects of continuous flow LVAD implantation complicated by RVF was simulated and then the effects of ASD, CPC, CAS and RVAD treatments were simulated for each patient., Results: The model successfully reproduced patients' baseline and the hemodynamic effects of the surgical strategies. Simulating the different surgical strategies, an unloading of the right ventricle and an increment of left ventricular preload were observed with an improvement of the hemodynamics (total cardiac output: ASD +15%, CPC +10%, CAS +70% RVAD +20%; right ventricular external work: ASD -19%, CPC -46%, CAS -76%, RVAD -32%; left ventricular external work: ASD +12%, CPC +28%, RVAD +64%)., Conclusions: The use of numerical model could offer an additional support for clinical decision-making, also potentially reducing animal experiments, to compare the outcome of different surgical strategies to treat RVF in LVAD.

The aim of this work is to develop a tool to study the effect of sodium nitroprusside (SNP) on hemodynamics in conjunction with baroreflex and mechanical circulatory assistance. To this aim, a numerical model of the pharmacodynamic effect of SNP was developed and inserted into a cardiovascular circulatory model integrated with baroreflex and LVAD (continuous flow pump with atrio-aortic connection) sub-models.The experiments were carried out in two steps. In the first step the model was verified comparing simulations with experimental data acquired from mongrel dogs on mean arterial pressure (MAP), cardiac output (CO), heart rate (HR), peripheral resistance, and left ventricular properties.In the second step, the combined action of SNP and mechanical circulatory assistance was studied. Data were measured at pump off and at pump on (20000 rpm and 24000 rpm). At pump off, with a 2.5 µg/kg per min SNP infusion in heart failure condition, the MAP was reduced by approximately 8%, CO and HR increased by about 16% and 18%, respectively. In contrast, during assistance (24000 rpm) the changes in MAP, CO and HR were around -9%, +12%, and +20%, respectively. Furthermore, the effects of the drug on hemodynamic parameters at different heart conditions were significantly different. Thus, the model provides insight into the complex interactions between baroreflex, drug infusion, and LVAD and could be a support for clinical decision-making in cardiovascular pathologies.

Purpose: VADs could be used for transportation of the great arteries (TGA) and for congenitally corrected transposition (ccTGA) treatment. A cardiovascular numerical model (NM) may offer a useful clinical support in these complex physiopathologies. This work aims at developing and preliminarily verifying a NM of ccTGA and TGA interacting with VADs., Methods: Hemodynamic data were collected at the baseline (BL) and three months (FUP) after apical (atrio-aortic) VAD implantation in a TGA (ccTGA) patient and used in a lumped parameter NM to simulate the patient's physiopathology. Measured (MS) and simulated (SIM) data were compared., Results: MS and SIM data are in accordance at the BL and at FUP. Cardiac output (l/min): BL_m = 2.9 ± 0.4, BL_s = 3.0 ± 0.3; FUP_m = 4.2 ± 0.2, FUP_s = 4.1 ± 0.1. Right atrial pressure (mmHg): BL_m = 21.4 ± 4.1, BL_s = 18.5 ± 4.5; FUP_m = 13 ± 4, FUP_s = 14.8 ± 3.6. Pulmonary arterial pressure (mmHg): BL_m = 56 ± 6.3,BL_s = 57 ± 2, FUP_m = 37.5 ± 7.5, FUP_s = 35.5 ± 5.9. Systemic arterial pressure (mmHg): BL_m = 71 ± 2, BL_s = 74.6 ± 2.1; FUP_m = 84 ± 9, FUP_s = 81.9 ± 9.8., Conclusions: NM can simulate the effect of a VAD in complex physiopathologies, with the inclusion of changes in circulatory parameters during the acute phase and at FUP. The simulation of differently assisted physiopathologies offers a useful support for clinicians.

Introduction: The aim of this study was to investigate the effects of the intra aortic balloon pump (IABP) and of aortic compliance on left ventricular performance, including the effects of baroreflex control.
, Methods: The study was conducted using a hybrid cardiovascular simulator, including a computational cardiovascular sub-model, a hydraulic sub-model of the descending aorta, and a baroreflex computational sub-model. A 40 cc balloon was inserted into a rubber tube component of the hydraulic sub-model. A comparative analysis was conducted for two aortic compliances (C1 = 2.4 and C2 = 1.43 cm3/mmHg, corresponding to an aortic pulse pressure of 23 mmHg and 35 mmHg, respectively), driving the balloon for different trigger timings.
, Results: Under C1 conditions, the IABP induced higher effects on baroreflex activity (decrement of sympathetic efferent activity: 10% for C1 and 14.7% for C2) and ventricular performance (increment of cardiac output (CO): 3.7% for C1 and 5.2% for C2, increment of endocardial viability ratio (EVR): 24.8% for C1 and 55% for C2). The best balloon timing was different for C1 and C2: inflation trigger timing (from the dicrotic notch) -0.09 s for C1 and -0.04 s for C2, inflation duration 0.25 s for C1 and 0.2 s for C2.
, Conclusions: Early inflation ensures better EVR, CO, and an increment of the afferent nerve activity, hence causing peripheral resistance and heart rate to decrease. The best balloon timing depends on aortic compliance, thus suggesting the need for a therapy tailored to the specific conditions of individual patients.

The pulsatile catheter pump (PUCA pump) is a left ventricular assist device that provides additional flow to the left ventricle. It is usually run in order to ensure a counterpulsation effect, as in the case of the intra-aortic balloon pump (IABP). Because of this similarity, a comparison between the PUCA pump and the IABP was conducted from both the hemodynamic and energetic points of view. Numerical models of the two devices were created and connected to the CARDIOSIM cardiovascular simulator. The PUCA and IABP models were then verified using in vivo experimental data and literature data, respectively. Numerical experiments were conducted for different values of left ventricular end systolic elastance (Els) and systemic arterial compliance (Csa). The energetic comparison was conducted taking into account the diastolic pressure time index and the endocardial viability ratio. Hemodynamic results expressed as cardiac output (CO) and mean coronary blood flow (CBF) show that both the IABP and the PUCA pump efficacy decrease with higher values of Els and Csa. The IABP especially shows higher sensitivity to these parameters, to the extent that in some cases CO actually drops and CBF does not increase. On the other hand, for lower values of Csa, IABP performance improves so much that the PUCA pump flow needs to be increased in order to ensure a hemodynamic effect comparable to that of the IABP. Energetic results show a trend similar to the hemodynamic ones. The study will be continued by investigating other energetic variables and the autonomic response of the cardiovascular system.